colorbar for scatter shows no negatives values...

[gil]

Hi everyone !

i made a program that should give me a beautiful graph with X, Y and color for the Z variable. But the color only gives me positive values, and not the negatives. I print my Z values and there are many negatives, so i should have it but i don't....

here is my program, i would be grateful if you can help me :

import numpy as np
import matplotlib.pyplot as plt
data = np.loadtxt("table2.txt")
print (data[2,0])
x=data[:,23]
y=data[:,20]
Z=data[:,0]
plt.scatter(x,y,Z,cmap='jet')
plt.colorbar()
plt.show()